The copending application of Lohmann et al Ser. No. 968,652 has a fuel injection system which, by delineating the primary and secondary combustion zones and making possible the maintenance of optimum equivalence ratio in each zone over the entire combustion range, thereby effectively reduces undesirable emissions in the exhaust gas. Any improvements to the flow of fuel and air, the mixing of the air and fuel to further enhance engine performance will help to reduce the quantity of undesirable emissions beyond that accomplished in this injection system.